; class Acanthodii)
One of the larger orders of fossil fish that had bony jaws and body skeleton, ganoid scales, a heterocercal tail, and stout spines located before the dorsal, anal, pectoral, and pelvic fins. One of the better-known forms, Climatius, carried five additional pairs of fins along the belly and reached a length of only 8 cm. These fish may actually be half-way between the sharks and the bony fish.
Subjects: Earth Sciences and Geography — Zoology and Animal Sciences.